1. Field of the Invention
Liquified gases such as oxygen, nitrogen, argon, or carbon dioxide are stored and transported in insulated cryogenic cylinders. These cylinders are filled and refilled from insulated storage tanks. The present invention relates to a device for reducing filling losses and vent noise, for example, while gravity filling cryogenic cylinders from a storage tank. The device is small and light weight and is easily assembled or disassembled to or form cryogenic cylinders.
2. Description of the Prior Art
There are a number of methods for filling cryogenic cylinders from a storage tank. Most such methods incur filling losses in the range of 10% to 30% of product being filled. Several prior art systems have attempted to reduce these filling losses. These prior art systems are elaborate, comparatively expensive, and not satisfactory. Most of these use pumps for the filling process such as top filling with pumps, and recirculating systems. Another method uses an automatic throttling valve and pressure sensor to maintain system pressure close to the pressure of liquid in the storage tank.
For top filling with pumps to work effectively, the cryogenic cylinder as well as the lines and plumbing between storage tank and cryogenic cylinder needs to be cold. This means that cylinders left empty for some time can not be used effectively. Additional issues would be those of pump maintenance and need for periodic blow downs of cylinders in order to maintain pump prime.
The recirculating system uses a pump and recirculates the flashed vapor back to a storage tank. There is the potential of contaminating the storage tank if a contaminated liquid cylinder is being filled. Here again, higher pump maintenance is expected.
The system with an automatic throttling valve uses a pressure sensor for sensing the vapor pressure in the storage tank. This sensed vapor pressure of the storage tank is communicated to the automatic throttling valve which permits the vapor from the cylinder to vent to the atmosphere at a preset pressure differential. Again, this system is complex and expensive.